1. Joe Levine’s Purple Haze

4. Physical/Phenomenal Gaps
P = the complete microphysical truth
Q = a phenomenal truth
Q1: Is there an epistemic gap between P and Q?
Q2: Is there an ontological gap between P and Q?

5. The Conceivability Argument
(1) P&~Q is conceivable
(2) If P&~Q is conceivable, P&~Q is possible.
(3) If P&~Q is possible, materialism is false.
___________
(4) Materialism is false.

7. Refinement 1 (1) P&~Q is ideally conceivable
(2) If P&~Q is ideally conceivable, P&~Q is primarily possible.
(3) If P&~Q is primarily possible, materialism is false.
___________
(4) Materialism is false.

8. Refinement 2 (1) ‘pq’ is ideally conceivable
(2) If ‘pq’ is ideally conceivable, p and q have distinct properties as MOPs.
(3) If p and q have distinct properties as MOPs [for all p], materialism is false.
___________
(4) Materialism is false.

9. The Conceivability Argument
(1) P&~Q is conceivable
(2) If P&~Q is conceivable, P&~Q is possible.
(3) If P&~Q is possible, materialism is false.
___________
(4) Materialism is false.

10. Type-A and Type-B Materialism
Type-A materialist: denies premise (1)
No (ideal) epistemic gap
P&~Q conceivable
Type-B materialist: denies premise (2)
Epistemic gap but no ontological gap
P&~Q conceivable but not possible

13. E-Type and NE-Type Materialists
NE-type (non-exceptionalists): The phenomenal case is not special
Epistemic gap between P and Q (conceivability of P&~Q) is analogous to gaps in other domains
“Water zombies” (P&~W) are conceivable too
E-type (exceptionalists) The phenomenal case is special
The epistemic gap between P and Q (conceivability is not analogous to epistemic gaps in other domains.
Water zombies aren’t conceivable.

14. Puzzle Joe says he’s an NE-type materialist.
But he also thinks there’s a special explanatory gap in the case of consciousness, manifested in the conceivability of zombies.
So presumably he thinks there’s a sense in which zombies are conceivable but water-zombies are not.
Doesn’t this force him to be E-type?

15. Partial Answer Joe distinguishes thin and thick conceivability.
Both zombies and water-zombies are thinly conceivable:
No formal/conceptual contradiction in P&~Q or P&~W.
Zombies but not water-zombies are thickly conceivable.
P is thickly conceivable iff P plus “non-gappy identities” is thinly conceivable
Water-zombies are ruled out by adding non-gappy identity (water = H2O)
Ruling out zombies requires adding “gappy” identity p=q

16. Priority?
The notion of thick conceivability is derivative on notion of an explanatory gap. Is this the right way around?
(1) Plenty of people (including Levine 1983?) argue from conceivability of zombies to an explanatory gap
(2) Intuitively, there’s a fairly pretheoretical sense of conceivability in which zombies but not water-zombies are conceivable.
(3) Joe’s approach puts a lot of weight on the notion of “gappy identity” – problematic?

17. Positive Conceivability
Desirable: zombies (not not water-zombies) are conceivable in a sense that isn’t definitionally dependent on e-gap.
My view: zombies (but not water-zombies) are positively conceivable:
one can imagine zombies, form a positive conception of them, imagine a world containing them, etc.
Joe can reasonably hold this too

18. Positive/Negative Conceivability
Joe’s view: water-zombies are thinly but not thickly conceivable
Close to: water-zombies are negatively conceivability (~P is not a priori) but not positively conceivable (not imaginable).

19. Two Conceivability Arguments
Positive conceivability argument (PCA):
(1) Zombies are positively conceivable
(2) Positive conceivability entails possibility
(3) Zombies are possible
Negative conceivability argument (NCA):
(1) Zombies are negatively conceivable
(2) Negative conceivability entails possibility

20. Divided Response In effect, Joe must give
E-type response to the positive conceivability argument
NE-type response to the negative conceivability argument.

21. Positive Conceivability Argument
Joe: zombies (but not water-zombies) are thickly (positively?) conceivable
So needs to give E-type response here.
But doesn’t give any such response
In fact, says that E-type responses are “can easily seem to be ad hoc”?
Q: Why isn’t Joe (in effect) forced to be equally ad hoc in responding to PCA? And how will this be justified?

22. Negative Conceivability Argument
Joe: Water-zombies are negatively conceivable too.
There is no a priori entailment from P to W
‘Water’, ‘consciousness’, etc, all have non-ascriptive modes of presentations
They support very few a priori/conceptual connections

23. A Priori Entailments
My view: there are a priori entailments from PQTI (physics, qualia, that’s-all, indexicals) to W (water-truths)
See Chalmers and Jackson 2001
Basic idea: knowing PQTI enables one to know macro truths about appearance, behavior, composition, distribution, etc, which enables one to know truths about water, without further empirical information.

24. Joe’s View
Levine 1993 accepts “quasi-analytic” entailment of water-truths by underlying truths.
Levine 2002 denies an a priori/analytic entailment.
He concedes some strong epistemic disanalogies between deducibility of water and consciousness truths, though:
Allows “armchair” knowability of water-truths but not consciousness-truths without further empirical work.
Knowledge argument also provides disanalogy in knowability of water/consciousness truths given base truths?

27. Semantic/Substantive Questions
Further Joe elsewhere articulates a disanalogy between questions about consciousness and about (e.g.) water, given full knowledge of underlying facts:
Questions about consciousness are “substantive”
Questions about water are “semantic”
Cf: Carnapian questions of fact and of meaning?
Suggests something reminiscent of a conceptual/semantic entailment in one case but not the other
I think: this situation yields a priori entailment
At least, is a strong epistemic disanalogy that deserves attention in analyzing the conceivability argument.

28. Theory of Reference?
Joe suggests briefly: these judgments about high-level truth and reference may be mediated by theory of reference, which is a posteriori
Response:
(1) Judgments about cases aren’t mediated by theory of reference; rather, knowledge of theory of reference is mediated by judgments about cases
(2) The theory of reference is in the relevant sense a priori, since we can arrive at it by non-empirical reflection on ways the world might turn out
(3) When the theory of reference is responsive to empirical information, we still have an a priori inferences from the empirical information to the conclusion about reference.

29. Psychoanalytic Conclusion
Joe’s torment: how to reconcile the highly distinctive epistemic gap with the absence of an ontological gap?
His official NE-type response allows him to paper over the epistemic gap in this context.
But deep down Joe is really E-type: there’s a distinctive epistemic gap with respect to both consciousness and deducibility.
So, Joe needs to either (i) come out of the closet as an E-type responder (and give the response), or (ii) accept his glorious destiny as an anti-physicalist.